it looks like your server configuration doesn't allow to run the script long enough to create full sitemap. Please try to increase memory_limit and max_execution_time settings in php configuration at your host (php.ini file) or contact hosting support regarding this.

The host won't let me. They say it is not within their policy and will only alow me the 9000 for 24 hours. In any case the page doesn't run for more than 2 minutes so there must be something else wrong